Graphene—a two-dimensional sheet of carbon one atom thick—is exciting stuff. Combining good electrical properties, flexibility, mechanical strength, and other advantages, graphene can seem like a miracle material, especially when potential applications are listed. Talk of graphene-based protective coatings, flexible transparent electronics, super powerful capacitors, and so forth may seem like something from a Neal Stephenson science fiction novel, but they've all been seriously considered.

The material's potential is so high that its discovery merited the 2010 Nobel Prize in physics, awarded to Andre Geim and Konstantin Novoselov. Certainly my fellow Ars Technica writers and I have spilled a lot of digital ink on the subject.

However, with so much excitement, you would be forgiven for wondering if at least some of it is hype. (After all, graphene has been around for a number of years, but we don't have our transparent computers yet.) For this reason, Nobel Laureate Konstantin Novoselov and colleagues have written a critical, yet optimistic, assessment of the state of graphene research and production.

As they point out, there is a big question that must be answered before widespread adoption of graphene technology is possible: are graphene's advantages sufficient to use it in place of the materials we use in existing devices? The authors conclude that, to some extent, that's the wrong question. Graphene's biggest promise lies in novel applications, designed especially for the advantages that graphene offers.

What's the big deal about graphene?

Graphene was the first material discovered that consists of a single layer of atoms. (Other single-layer materials, including boron nitride and molybdenum disulphide, were subsequently discovered. In fact, graphene and boron nitride together have proven to be an effective composite material.) As shown in the scanning microscope image above, graphene forms a hexagonal lattice of carbon atoms. Multiple layers of graphene form the familiar substance graphite, used in pencils and as a mechanical lubricant; carbon nanotubes are graphene sheets rolled into a cylinder.

Due to the nature of the bonds between the carbon atoms, graphene is very resilient: the sheets can be bent at severe angles before fracturing and withstand high pressure. Since the material consists of only one layer of atoms, electron motion is confined to a single plane, which gives rise to novel electrical properties. Graphene is also transparent at optical wavelengths, and impervious to gas. Together, these properties make graphene desirable in protective films, as well as transparent, flexible electronic devices.

Production methods, costs, and quality

The amazing research we've seen being performed with graphene has all relied upon high-quality samples. As you might expect, achieving the best electrical and mechanical properties requires the most expensive and painstaking process: mechanical exofoliation. In this technique, graphene flakes are individually extracted using adhesive tape. This process is not scalable, so it is essentially useless in manufacturing terms.

Other methods are far more scalable, but currently trade off on quality.

Liquid-phase exfoliation involves suspending carbon-carrying materials (such as graphite) in a liquid with high surface tension, then bombarding the suspension with sound to extract graphene flakes.

Chemical vapor deposition (CVD) condenses a volatile substance containing carbon onto a copper surface. The graphene layer that forms can then be peeled off onto another substrate. CVD is frequently used to make other thin-film systems for electronic devices.

Growing graphene directly onto a silicon carbide wafer by selectively extracting the silicon atoms in the top layer via sublimation (vaporizing a solid).

This list isn't exhaustive, but it shows that many methods are available. While none of them currently produce as high quality graphene as mechanical exfoliation, CVD in particular is a promising method, and much less expensive.

Not all of these methods are equally useful for all applications, though. Some are best for making protective coatings, while others (which I've focused on here) are better for electronics, particularly nanoelectronics.

Where's my bendy laptop?

Beyond fabrication costs and quality, graphene-based electronics must overcome certain obstacles to be practical. Touch screens, electronic "paper", and other display-based media require improvements in the electrical resistance at the junction between the graphene and metal electrodes. The authors of the review wrote that they expect this problem will be solved in the next decade.

So why can't we make the whole device from graphene? While some progress has been made on graphene transistors, they aren't production-ready yet. Semiconductor transistors, which are the foundation of modern electronics, have a particular electronic property known as a bandgap: a transition point that allows an asymmetric flow of charge through circuits. Pure graphene lacks a bandgap; research is ongoing to address the problem (by using multiple layers, adding other elements, and/or making structural changes), but Novoselov et al. speculated graphene integrated circuits are at least a decade off.

As a result, graphene is not poised to replace conventional semiconductor components any time soon. However, in areas where no conventional devices exist—flexible and transparent electronics—graphene-based electronics could arrive in consumers' hands in the next decade or so. Maybe it won't be a bendable cell phone you can put in the back pocket of your jeans, but it's a safe bet that graphene will be moving from the laboratory into the wider world relatively soon.

33 Reader Comments

it's a safe bet that graphene will be moving from the laboratory into the wider world [of electronics] relatively soon.

Perhaps for some definitions of "very soon". Carbon nanotubes have had that 'they'll be there any day now' label applied to them for what? almost a decade longer than graphene? Just as with CNTs, it may be in mechanical applications (i.e. composites) that graphene will find practical application soonest.

it's a safe bet that graphene will be moving from the laboratory into the wider world [of electronics] relatively soon.

Perhaps for some definitions of "very soon". Carbon nanotubes have had that 'they'll be there any day now' label applied to them for what? almost a decade longer than graphene? Just as with CNTs, it may be in mechanical applications (i.e. composites) that graphene will find practical application soonest.

Read the definition of 'very soon' as about the same time when all this exciting new battery technology we've been hearing about actually makes it out of the lab and into consumers hands. They're both there, right over the horizon, you can almost see them if you squint real hard.

All else aside, it's pretty exciting technology, graphene materials and carbon nanotubes might be the next big leap in materials-technology that allow us to advance aircraft and spaceflight technology.

I seem to recall a calculation that a space-elevator would be theoretically possible if we built it from carbon nanotubes. Doubt we will see something like that in my lifetime, but it shows the incredible strength of the materials we could design if we get the volume-production aspects figured out.

Aren't carbon nanotubes associated with cancer risk, akin to asbestos? I am not an expert, just pointing out what i read in the regular press (which i acknowledge is not the best at conveying results of scientific research).

I suspect that would be a bigger roadblock to wider adoption than anything else.

Beyond fabrication costs and quality, graphene-based electronics must overcome certain obstacles to be practical. Touch screens, electronic "paper", and other display-based media require improvements in the electrical resistance at the junction between the graphene and metal electrodes. The authors of the review wrote that they expect this problem will be solved in the next decade.

The next decade? That's all wrong, the prototypical development cycle is 5 years.

I'm curious to know which other dimension they have left out to make it two-dimensional, width or depth?

OK, I know you're not serious, but like everyone's long-winded grandfather, I just have to butt in and blather on about dimensionality in materials.

Graphene is called a 2D material because of how extremely thin it is. Yes, it is still (at least) an atom thick, but electrons running about in a graphene layer are strongly confined in one direction (they can't easily go up or down to escape the graphene), but have almost no barrier to motion in the other two directions (within the plane of the graphene).

You can add more layers to graphene (people are constantly playing with bilayers, trilayers, and more, partly out of genuine curiosity, and partly because whenever you try to grow graphene monolayers you'll end up with a bunch of thicker areas thanks to random fluctuations in your growth or deposition process), and as you do so it starts to resemble a bulk (3D) material more and more. Eventually when you add enough layers, electrons are no longer strongly confined in the vertical dimension, and you lose some of the neat properties of your graphene sheet.

You could go the other way, however, and take your graphene sheet, and shrink one dimension of it, so you have a long, thin ribbon of the stuff. If the ribbon is thin enough, electrons will be strongly confined in two dimensions, but free to run along the length of the ribbon -- now you've got a 1D material! Graphene folks refer to these as nanoribbons, but in other materials they're simply called nanowires.

But wait, there's more! Shrink that ribbon down to a small island, and you end up with strong confinement of electrons in ALL dimensions! Now you have a 0D material, or a quantum dot.

Of course all of these configurations do have a height, a width, and a depth (or whatever else you want to call the three dimensions) -- it's just that these dimensions are small compared to the wavelength of an electron in the material.

By confining electrons in progressively more dimensions, we restrict their degrees of freedom and limit the number of possible states an electron in the material can occupy. One effect of this is to change the way light is absorbed by the material -- instead of a broad, smooth absorption vs wavelength curve, we end up with quantized absorption (See Britney Spears et al for more information: http://britneyspears.ac/physics/dos/dos.htm). As the article mentioned, the primary reason to use a 1D ribbon of graphene is to open up a bandgap (graphene is normally great at conducting, but to develop a good transistor we need to be able to turn it off at some point), which brings me to a completely new unsolicited wall of text, so we'll save that for another day.

The on/off ratio of graphene is currently terrible (~100 in this paper: http://pubs.acs.org/doi/abs/10.1021/nl9039636). The three properties that gave CMOS the huge edge over BJT devices was 1) size, 2) capacitive gates, and 3) an on/off ratios of >100,000. Until that changes, graphene wont have any chance of being used for processors.

Several years ago, someone invented the LASER.At the time, nobody knew exactly what to do with it - an answer looking for a question, as it were.It required the development of several other technologies to bring the LASER into it's own as a staple of contemporary life. Graphene is like that. Knowing that graphene exists and that it offers the characteristics that it does will stimulate and evolve applications that simply aren't immediately visible.IMHO: More "Attaboys!" to the researchers and fewer "Angels dancing on pinheads".

With dwindling helium supplies, I think graphene is a great material for Airships to prevent wasteful helium leakage that can never be recovered.

The above article also talks about graphene's strange property to selectively pass through water and only water. There must be plenty of low energy filtration, distillation applications. I envision zero energy diffusion based clean water production from contaminated sources in improvised places with no access to electricity, for example.

Oh carbon, how wonderful you are---six protons and twelve nucleons oh diamond that dazzlesoh nanotubes that never bucklesoh graphene sheets with miracle after miracle---slippery, super capacitive and conducts like wild Turning our wheels is fossil fuel we call crude oilCarbon in every DNA strand form a spiral---and here we are, in awe with the science of material

I'm curious to know which other dimension they have left out to make it two-dimensional, width or depth?

You know what I love? Pedantic nerds. Especially if they create a new account just to be pedantic.

It's pretty clear how the sheet could be two dimensional and a google search shows it to be a common and acceptable use. As a pedant you must hate that term.

Hooray for you! You discovered a new word and used it 3 times in your post, which means you've mastered it. Now move on to a new word before you risk becoming the definition of the word you're stuck on...With regard to dimensionality, it would be considered 2-dimensional if it can't complete a cycle of action away from the surface of the material. The greatest immediate interest would be its' use in a super-capacitor.

I'm curious to know which other dimension they have left out to make it two-dimensional, width or depth?

I don't see your joke if it is a joke, if you parameterize the location of the carbon atoms, they can be described by only 2 coordinates, that's 2 dimensional.

There's no such thing as a 2 dimensional object, as we all know. I imagine that if we consider an electron a point, then it's a 1 dimensional object. But even that isn't certain, as physicists hate infinities, and Plank space doesn't seem to allow it.

There's no such thing as a 2 dimensional object, as we all know. I imagine that if we consider an electron a point, then it's a 1 dimensional object. But even that isn't certain, as physicists hate infinities, and Plank space doesn't seem to allow it.

Naturally, even an electron has dimensions (and they're MUCH larger than the planck scale). The relevant thing here is the wavelength of the electron. In introductory physics classes we all learn that electrons are little hard spheres orbiting around a nucleus, kind of like how the moon orbits the earth. This picture is fine for most people -- it gives you a framework to talk about electron orbitals and valence electrons and all that -- but if you want to really understand the microscopic behavior of materials you need to go deeper.

Electrons aren't actually little hard spheres flying around in a material -- they're actually quantum objects, with a wavelength and all. Normally the electron wavelength is so small that it just isn't relevant -- if you have a material that's more than a few wavelengths wide then you can get away with describing the electron classically, as a (mostly) Newtonian particle.

If, however, you restrict the electron to a space comparable to the wavelength, you start to see some very interesting properties. Now the electron cannot freely move in any direction at any speed -- instead there are precisely defined energy levels that the electron can have, which lead to very different behavior than you would expect classically.

So in a nutshell, generally we call a material 0D, 1D, or 2D, when we've restricted its electrons to move in that many dimensions. For example, in a 2D material, electrons are free to move normally in two dimensions, but are quantum mechanically confined in the other dimension.

It generally takes 10 tp 20 years for a new, basic discovery to become a production able technology. If this becomes practical by 2020, that would be good.

Yep, 10-20 is about right. Note that production methods for graphene are very similar to those used in carbon nanotube (CNT) work, so there's some head start for people/companies working with graphene. Another advantage is that graphene comes in one "flavor", whereas batches of CNTs typically contain mixtures of metallic and semiconducting tubes (and not with the same bandgap).

There is a good chance that first commercial applications of graphene will be in composite materials and then in transparent electrodes.

The on/off ratio of graphene is currently terrible (~100 in this paper: http://pubs.acs.org/doi/abs/10.1021/nl9039636). The three properties that gave CMOS the huge edge over BJT devices was 1) size, 2) capacitive gates, and 3) an on/off ratios of >100,000. Until that changes, graphene wont have any chance of being used for processors.

Maybe this is of interest. Maybe it's not. But the structure Samsung created seems to have the needed on/off ratio.

The image caption incorrectly states that the image is a scanning electron micrograph. Scanning electron microscopes are not able to resolve individual atoms. The caption on the source website indicates that the image was in fact obtained through (aberration-corrected) transmission electron microscopy.

Oh carbon, how wonderful you are---twelve protons and twelve apostlesbecome diamonds that dazzles every girlbecome Nanotubes that never bucklesbecome Graphene sheets with miracle after miracle---slippery, super capacitive and conducts like wild Turning our wheels is fossil fuel we call crude oilCarbon in every DNA strand form a spiral---and here we are, in awe with the science of material

A neutral Carbon 12 (C_12) atom has six protons, six neutrons and just as many electrons (last time I checked)

Oh carbon, how wonderful you are---twelve protons and twelve apostlesbecome diamonds that dazzles every girlbecome Nanotubes that never bucklesbecome Graphene sheets with miracle after miracle---slippery, super capacitive and conducts like wild Turning our wheels is fossil fuel we call crude oilCarbon in every DNA strand form a spiral---and here we are, in awe with the science of material

A neutral Carbon 12 (C_12) atom has six protons, six neutrons and just as many electrons (last time I checked)

I'm curious to know which other dimension they have left out to make it two-dimensional, width or depth?

I don't see your joke if it is a joke, if you parameterize the location of the carbon atoms, they can be described by only 2 coordinates, that's 2 dimensional.

There's no such thing as a 2 dimensional object, as we all know. I imagine that if we consider an electron a point, then it's a 1 dimensional object. But even that isn't certain, as physicists hate infinities, and Plank space doesn't seem to allow it.

You are missing the point, it is perfectly acceptable in Mathematics or Information theory to describe dimensions by number of parameters. If you have an array of particles lying on x-y plane, you call it two dimension. Yes straightly speaking it exists as 3 dimensional object in reality, as nothing is infinitesimal, but that is just plain pedantic.

It took a lot of basic research before transistors became mainstream technology in the 1950s, and years before they became ubiquitous. I don't see why graphene would be different. We're still very much at the experimental "Hey, what if I do this?" stage. It's fun to watch, IMO.

You are missing the point, it is perfectly acceptable in Mathematics or Information theory to describe dimensions by number of parameters. If you have an array of particles lying on x-y plane, you call it two dimension. Yes straightly speaking it exists as 3 dimensional object in reality, as nothing is infinitesimal, but that is just plain pedantic.

"Pedantic" in that particularly Internet way, where you say something is wrong based on a precise definition as it applies to a specific context, ignoring 1) that other contextual definitions exist and 2) in one such context, which also happens to be more applicable to the situation at hand, the original usage was completely correct.

I think this form of pedantry could be usefully replaced with the term "deliberately obtuse".

The image caption incorrectly states that the image is a scanning electron micrograph. Scanning electron microscopes are not able to resolve individual atoms. The caption on the source website indicates that the image was in fact obtained through (aberration-corrected) transmission electron microscopy.

Well, I may be pedantic, but the atoms can be happily resolved in aberration corrected *scanning* transmission electron microscopy as well. That is a technique that is of course realized in a TEM.

But the TEAM 0.5 microscope at the NCEM in Berkeley has both probe and image corrector. Strictly speaking, it could be both.

Just to say that the caption of the image my bt partially correct after all. Still, it should be corrected.

Hello,The claim that there is no industrial scale method for high quality graphene production isn't true for about a year now. Please take a look at this article:http://pubs.acs.org/doi/abs/10.1021/nl200390eThe scientists behind this work are already preparing for industrial scale (commercial) production.

And as for the argument, found in the previous comments, whether or not graphene is two- or three-dimensional (to be honest I haven't read all of the comments):In physics, when someone says that a system is two dimensional he doesn't mean that it has only two physical dimensions. It's obvious that besides width and length the two dimensional lattice of atoms has a thickness of one atom (the depth - the third dimension). Such system is called two dimensional because:- in terms of theoretical physics, the physical model that is used to describe it's behavior is two dimensional- in real-world terms (or the experimental side of physics) the interactions between elements of the sysem are two dimensional, which has real-world effects on the physical properties of the system - all the cool stuff about graphene comes from the fact that the carbon atoms in the system interact only on the two dimensional plane (there just are no neighbours in the third dimension to interact with).Therefore, such systems as graphene are called two dimensional.

it's a safe bet that graphene will be moving from the laboratory into the wider world [of electronics] relatively soon.

Perhaps for some definitions of "very soon". Carbon nanotubes have had that 'they'll be there any day now' label applied to them for what? almost a decade longer than graphene? Just as with CNTs, it may be in mechanical applications (i.e. composites) that graphene will find practical application soonest.

Read the definition of 'very soon' as about the same time when all this exciting new battery technology we've been hearing about actually makes it out of the lab and into consumers hands. They're both there, right over the horizon, you can almost see them if you squint real hard.

Edit: <sigh....>

Depends on if you are talking about research of daily life product. Graphene is now widely investigated by industry (I should say more than CNT have ever been). A startup has already been founded in the silicon valley, that will produce flexible battery with longer lifetime. So far, they are few applications of graphene ( http://www.graphenea.com/blogs/news/725 ... pplication), like flexible and transparent electronics, or better batteries. This is already happening in the labs. I guess soon on the market too.